Integrated circuits such as computer chips are manufactured from semiconductor wafers. These wafers are subjected to numerous steps during the process of making integrated circuits. This generally entails transporting a plurality of wafers from one workstation to another for processing by specialized equipment. As part of the processing procedure, wafers may be temporarily stored or shipped in containers to other plants or to end users. Such intra-facility and extra-facility movements may generate or expose the wafers to potential wafer ruining contaminants. In order to reduce the deleterious effect of contaminants on wafers, specialized containers have been developed to minimize the generation of contaminants and to isolate wafers from contaminants exterior to the containers. A principal feature common to these containers is that they are provided with removable doors or closures to enable access to the wafers inside.
Plastic containers have been used for decades for transporting and storing wafers in-between process steps. Such containers have highly controlled tolerances for interfacing with processing equipment as well as the equipment/robots that transport the containers. Moreover, it is desirable in such plastic containers to use components that are attachable and removable without using metallic fasteners such as screws, since metal fasteners can cause particle generation when inserted and removed.
Additional, required or desirable characteristics of containers to transport and/or store semiconductor wafers include light weight, rigidity, cleanliness, limited gaseous emissions, and cost effective manufacturability. The containers provide hermetic or close to hermetic isolation of wafers when the containers are closed. Simply stated, such containers need to keep the wafers clean, uncontaminated, and undamaged. Additionally, carriers need to maintain their capabilities under the rigors of robotic handling which includes lifting the carrier by the robotic flange positioned at the top of the container as well as transporting such carriers by way of conveyor systems that engage conveyor flanges on outside surface of side walls of the containers.
Front opening wafer containers have become the industry standard for transporting and storing large diameter 300 mm wafers. In such containers the front door is latchable within a door frame of a container portion, and closes a front access opening through which the wafers are robotically inserted and removed. When the container is fully loaded with wafers the door is inserted into the door frame of the container portion and latched thereto. When seated, cushions on the door provide upward, downward, and inward constraint for the wafers.
The semiconductor industry is now moving toward using even larger, 450 mm diameter, wafers. The larger diameter wafers, although providing cost efficiencies, also provide increased fragility, greater weight, and present undiscovered issues associated with handling and storing the larger wafers in containers made of plastic. Deflection and related problems associated with the expanses of plastic on the top, bottom, sides, front, and back are exacerbated. Assembly of larger components and the manufacturing tolerances of the components being assembled are more problematic. Forces exerted by the increased weight of substrates on the larger components cause more stress, manufacturing tolerances are greater and conventional connection techniques between components may be inadequate or not optimum. For example where in smaller wafer carriers where loads are transmitted from one component to another, often locking structure, such as detents, are putting directly on one component or the other. See, for example, U.S. Pat. No. 7,370,764, illustrating load bearing handles slidingly attachable to shells using detents integral with the handle. This patent is owned by the owner of the instant application. When dealing with greater weights and larger components such configurations may not be optimal.
Wafers of larger dimensions also have significantly greater sag which will make them more susceptible to damage during handling and transport and require unique support not required for smaller wafers. This greater sag presents challenges in maintaining the desired spacing between wafers while still allowing placement and removal of the wafers robotically by robotic arms.
In conventional 300 mm wafer containers, particularly those known as FOSBS (front opening shipping boxes) the front door is latchable to a container portion and closes a front access opening through which the wafers are robotically inserted and removed. When the container is fully loaded with wafers the door is inserted into the door frame of the container portion and latched thereto. In such a configuration the wafers have a first horizontal seating position on the laterally placed shelves and then, upon insertion of the door, the wafers are vertically elevated to a second seating position by wafer supports with angled ramps at the rear of the wafer container as well as wafer supports, often referred to as “cushions”, on the inside surface of the door. The container may then be rotated rearwardly 90 degrees to orient the wafers vertically for shipping. See U.S. Pat. Nos. 6,267,245 and 6,010,008 which are owned by the owner of the present application and which are hereby incorporated by reference. The angled ramps are part of V-shaped grooves, with the V rotated 90 degrees, whereby the lower leg of the V engages the wafer edge and rides up the inclination of the lower leg as the door is being inserted, ultimately seating at the inside apex of the V-shaped groove. When seated the cushions on the door then provide upward, downward, and inward constraint. With the greater sag associated with 450 mm wafers, conventional ramps as illustrated in U.S. Pat. No. 6,010,008 may not be optimal.
Along with increasing size of semiconductor wafers, the density of the circuits formed on the wafers has also been increasing, making the circuits more susceptible to defects from smaller and smaller particles and other contaminants. In short, as wafers have increased in size, containers have increased in size as well, and the requirements for keeping the wafers clean and contaminant free have become more stringent due to the wafers being more susceptible to smaller particles and other contaminants.
Accordingly, a need in the industry exists for a wafer container that addresses one or more of these problems, particularly as they exist relative to containers for 450 mm diameter and larger wafers.